A picture viewer for paper pictures is found in German Auslegeschrift No. 22 12 135 and for (unexposed) photographic plates in German Auslegeschrift No. 224 700 to German Patent Specification No. 179 675.
Such devices are intended to present to an observer (or to a camera) the viewing side or the exposure side of a pile of picture or plates. After the viewing of illumination, the picture just viewed in pushed laterally away from the pile and pushed under the pile again on the other side of the pile. For this purpose the known devices have, basically, the following co-operating elements:
The pile--in the following reference is made only to a pile of pictures, although the principle applies equally to plates--is located in a housing having a viewing aperture which may be glazed. One narrow side of the housing is open, and through the aperture, between limit stops, a slider member may be moved such that when it is pulled out it takes with it by means of a transporter the picture arranged facing the viewing window. In this operation the picture concerned is guided over a member referred to here and hereinafter as a separator, by which a transverse bar is to be understood, which, near to the housing aperture for the slider member, leaves open only at the top and the bottom a slot for the picture to pass through. The transporter of the slider member, which is constructed like a hook, therefore takes with it only this one picture, whilst the remainder of the pile lies adjacent to the separator. During the return stroke of the slider member, or as it is re-inserted, the picture pulled away through the upper slot is pushed back again through the lower slot and in so doing goes under the pile. A pressure arrangement using a spring holds the pile and, in particular, the uppermost picture, against the viewing aperture.
In the known devices the entire housing is therefore closed on all sides with the exception of the viewing aperture--which is designed to be smaller than the pictures--and the separator slots and passages for the slider member already mentioned, so that to insert or remove a pile of pictures additional measures are necessary.
In the two known constructions mentioned first, the housing base may be detachable or may be hinged back, and in the last construction mentioned the housing has a closable insertion aperture on the narrow side opposite the slider member. In a further known construction according to German Patent Specification No. 873 908 (which otherwise belongs to the type described) not only is one such a lateral aperture provided, but it is arranged that an entire magazine of pictures can be exchanged.
These means for inserting or removing a pile are not only expensive but also complicated to handle.